Displays such as a cathode ray tube (CRT also known as Braun tube) display, a liquid crystal display(LCD), a plasma display panel(PDP) and an electroluminescent display(ELD), etc., have been conventionally used in the art.
Among them, a CRT display has been most widely used in TV, computer terminal, etc., since it has advantages over the others in light of display quality and economical efficiency, etc. CRT which is a vacuum tube consisting of an electron beam emission part, an electron beam modulation part, an electron beam deflection part and an electron beam activation part, works on the following principle: thermionic beam emitted from a cathode is concentrated and accelerated into a form of thin beam by electron lens system, and deflected to collide with phosphor coating the inner part of frontal vacuum tube, which finally activates the phosphor to give luminscence. Though CRT has advantages of high brightness, good color and display contrast, and easy scanning and modulation, it has revealed a critical shortcoming that the larger a screen is, the heavier and larger the CRT is.
Though studies on a flat-plane CRT display have been carried out to overcome the said problems appeared in the CRT, remarkable results have not been obtained. For example, a flat CRT which employs microchannel plate(MCP) has been suggested in the art, however, it has not been commercialized, since it, like the conventional CRTs, utilizes the method for electron emission using one electron gun, and travelling path of electrons is complex, which raises an obstacle in the enlargement of area.
LCD is a flat display using modulation of beam by liquid crystal, and has advantages over the conventional displays, in light of low electric power consumption and low operation voltage requirement. Since flat shape, light weight and colorized display can be realized in LCD, it has been widely used in a portable display, etc. However, LCD has also shortcomings that viewing angle is limited and utility of back light is low, since display contrast depends on viewing direction. Moreover, problems of poor operation at low temperatures and frequent deterioration of liquid crystal are inevitably raised in LCD, owing to the response characteristics depending on the surrounding temperature.
PDP is a flat display using luminiscence generated by D.C. (direct current) or A.C. (alternating current)-driven electric discharge of inert gas. It has advantages over the conventional displays, in light of thin film-like structure, high response speed, and increased display contrast. Moreover, use of phosphor permits colorized display, and developing into a large-area screen is facilitated. However, since PDP utilizes plasma discharge generating in minute space, size of pixel can not be decreased, which naturally limits the development of highly definite screen.
ELD is a display whose pixel is provided by electroluminescent device. The electroluminescent device, depending on luminescence mechanism, is classified into intrinsic and charge injection-type electroluminescent devices. In general, the intrinsic and charge injection-type electroluminescent devices are called as electroluminescent (EL) device and light emitting diode(LED), respectively, and a flat display using the intrinsic electroluminescent device is generally represented as "ELD". A flat display using EL device has an advantage that developing into a large-area screen is facilitated, and brightness of red(R) and green(G) is high. However, it has revealed shortcomings that brightness of blue(B) luminescent device is low, which blocks the development of perfectly colorized display.
Generally, LED is classified into bulk-type LED employing a crystalline semiconductor such as GaAs and thin film-type LED employing an amorphous semiconductor such as a-SiC or organic material. A flat display employing the bulk LED has a difficulty in performance of blue LED of high efficiency, which also blocks the development of perfectly colorized display. Also, a large-area screen can not be achieved, due to the employment of crystalline semiconductor. On the contrary, a flat display using the thin film LED realizes a large-area screen and perfect colorization, while it has a short life span, owing to early deteriorization of luminescence device.